src/share/vm/oops/oop.inline.hpp

rev 5729 : 8029396: PPC64 (part 212): Several memory ordering fixes in C-code.

@@ -488,13 +488,13 @@
 
 inline int oopDesc::size()  {
   return size_given_klass(klass());
 }
 
-inline void update_barrier_set(void* p, oop v) {
+inline void update_barrier_set(void* p, oop v, bool release = false) {
   assert(oopDesc::bs() != NULL, "Uninitialized bs in oop!");
-  oopDesc::bs()->write_ref_field(p, v);
+  oopDesc::bs()->write_ref_field(p, v, release);
 }
 
 template <class T> inline void update_barrier_set_pre(T* p, oop v) {
   oopDesc::bs()->write_ref_field_pre(p, v);
 }

@@ -503,19 +503,27 @@
   if (always_do_update_barrier) {
     oop_store((volatile T*)p, v);
   } else {
     update_barrier_set_pre(p, v);
     oopDesc::encode_store_heap_oop(p, v);
-    update_barrier_set((void*)p, v);  // cast away type
+    // always_do_update_barrier == false =>
+    // Either we are at a safepoint (in GC) or CMS is not used. In both
+    // cases it's unnecessary to mark the card as dirty with release sematics.
+    update_barrier_set((void*)p, v, false /* release */);  // cast away type
   }
 }
 
 template <class T> inline void oop_store(volatile T* p, oop v) {
   update_barrier_set_pre((T*)p, v);   // cast away volatile
   // Used by release_obj_field_put, so use release_store_ptr.
   oopDesc::release_encode_store_heap_oop(p, v);
-  update_barrier_set((void*)p, v);    // cast away type
+  // When using CMS we must mark the card corresponding to p as dirty
+  // with release sematics to prevent that CMS sees the dirty card but
+  // not the new value v at p due to reordering of the two
+  // stores. Note that CMS has a concurrent precleaning phase, where
+  // it reads the card table while the Java threads are running.
+  update_barrier_set((void*)p, v, true /* release */);    // cast away type
 }
 
 // Should replace *addr = oop assignments where addr type depends on UseCompressedOops
 // (without having to remember the function name this calls).
 inline void oop_store_raw(HeapWord* addr, oop value) {